The present invention relates to security systems. More particularly, the invention is directed to a child safety system.
A typical home or commercial security system generally consists of a plurality of different monitoring devices, depending upon the type and extent of protection desired. The monitoring devices include motion sensitive detectors, closed circuit video cameras, light curtains and audio detectors. Motion sensitive detectors and light curtains may be setup to cover a particular area. An alarm will be triggered if movement is detected within the monitoring area. Likewise, audio detectors will monitor for intruders by detecting all sounds within a defined area and activating an alarm if the sounds exceed a predetermined threshold.
Video monitoring devices such as closed circuit cameras are typically installed in areas where direct visual monitoring is difficult or when it is desired to observe several areas from a single location. However, video monitoring devices require constant visual surveillance of the display to determine whether any changes have occurred.
Electronic entry monitoring devices may be installed at all doors, windows or other access points within a home or commercial establishment. These devices utilize a closed current loop, whereby current is continuously circulated through the current loop as long as the door or window remains closed. Upon opening the monitored door or window, the current will be discontinued and the discontinuity triggers an alarm condition.
Although these prior art devices are useful for many applications, they may not be suitable in certain circumstances. For example, to implement a security system for children, such as in a daycare center to monitor whether children leave a predefined area or enter a restricted area, if only electronic entry monitoring devices or motion sensitive devices are used, an alarm will be triggered even if an adult or teacher opens a monitored door or enters a monitored area. There is a need for a system to enhance the security and safety of a daycare center or a home environment to monitor the whereabouts of every child.
U.S. Pat. No. 4,136,339 to Antenore discloses a perimeter alarm apparatus that includes a loop of wire to be placed around an area, and electrical circuitry which is connected to the loop to monitor a mobile signal sender within the loop. This system is designed to monitor one signal transmitter within the loop. Although the system may be modified to monitor more than one transmitter, it is necessary to duplicate the RF circuit tuned to the respective transmitter frequencies. This prior art design can only monitor a very limited number of transmitters because each transmitter, and thus each receiver, requires its own frequency range. It is costly and impractical to repeat circuitry for each additional transmitter. Moreover, the prior art does not disclose how to switch between the monitoring of different frequencies transmitted by different transmitters.
It is an objective of the present invention to enhance the safety of children in a predefined area, whereby each child can be individually monitored.
This and other objectives are achieved by providing a system having receiver communicating with a plurality of transmitters attached to target objects within a predefined perimeter area surrounded by a perimeter loop antenna. The system includes a scheme for identifying individual transmitters and for processing the detection of multiple identification signals sent therefrom. The system will alarm the operator if one of the monitoring objects either leaves the predefined perimeter or enters a restricted area.